The ITU has taken a big step in the standardization of G.fast, a broadband technology capable of achieving download speeds of up to 1Gbps over copper telephone wire.

By
Mikael Ricknäs
| Dec 12, 2013

| IDG News Service

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The ITU has taken a big step in the standardization of G.fast, a broadband technology capable of achieving download speeds of up to 1Gbps over copper telephone wire.

The death of copper and the ascent of fiber has long been discussed. However, the cost of rolling out fiber is still too high for many operators that instead want to upgrade their existing copper networks. So there is still a need for technologies that can complement fiber, including VDSL2 and G.fast.

The standardization of G.fast started in 2011, and has now reached what is known as first-stage approval or consent. That means the technical specification is ready to become standard. Next up is a comment period, and the standard is expected to be final by April next year, according to ITU.

"This is the most critical milestone in the process. The comments are designed to optimize the standard, not to reverse anything," said Michael Weissman, vice president of marketing at chip vendor Sckipio, which is focusing solely on silicon for G.fast.

The technology increases the bandwidth by using more spectrum, which could be compared to adding more lanes to a road. G.fast will use the 106MHz of spectrum, which compares to the 17MHz or 30MHz used by VDSL2 and the 40MHz used by the fastest LTE-Advanced networks currently being tested.

The drawback with G.fast is that it will only work over short distances, so 1Gbps will only be possible at distances of up to about 100 meters. The technology is being designed to work at distances up to 250 meters, though transmission speed is slower at that distace.

Similar to VDSL2, used to offer broadband at up to 100Mbps over copper, G.fast performance is affected by crosstalk interference. To counteract that, both use a technology called vectoring. It works by continuously analyzing the noise conditions on copper lines, and then creates a new, antinoise signal to cancel it out, much like noise-cancelling headphones. Without the use of vectoring, speeds offered by G.fast would drop from over 1Gbps to 200Mbps, according to Huawei Technologies.

Companies involved in its development have already tested the technology's capabilities through lab and field trials using prototype equipment based on drafts of the standard, according to ITU.

For example, in July Alcatel-Lucent and Telekom Austria completed the world's first trial of G.fast with vectoring using prototype equipment. The trial achieved a maximum speed of 1.1Gbps over 70 meters and 800Mbps over 100 meters over a single, good-quality cable, according to Alcatel-Lucent. On older, unshielded cables the trial managed 500Mbps over 100 meters on a single line, it said at the time. Since the performance has been improved by about 10 percent, according to Stefaan Vanhastel, marketing director for the Fixed Networks business at Alcatel-Lucent.

For Sckipio, the first-stage approval is the start of an intensive development period of production silicon that can be put in boxes, and used in the first commercial services by 2015.

"The complexity is in the modem ... The standard has got a lot in it, including the ability to do vectoring, handle large volumes of content and high frequencies. This is not a technology for the faint of heart," Weissman said.